After my last use of my modified 1.5kW hot plate I decided there had to be a better way. I had already retrofitted a decent power controller to the hot plate but it was still slow to heat and I had to dig out a thermometer to check temperature. The large 200mm (8") diameter seemed crazy for soldering boards that are only 30x10mm.
A search showed a nice device from Weller – but at just under $1000 I could not justify the expense. There is a good instructable using a large (100mm square) aluminium block with a cartridge heater and control system. Looks good but is quite bulky and a fair bit of work to make the controller. I looked at cartridge heaters (but none were small diameter), and then wondered about temperature measurement – and the solution appeared. A soldering iron heater is both small diameter and has a thermocouple. And (the good bit) – I can plug it into my existing soldering iron controller.
A check back to the Weller device showed that it worked in the same way – i.e. plugged into their soldering iron controller. The Weller device has a plate area of 50 x 80 mm, is 80W and a max temperature of 200C. It would be good to have a bit higher temperature range and use a more standard 50W iron controller. A quick back of the envelope sum, assuming heat loss is proportional to area and temperature suggested that a 40mm (1.5”) diameter plate should get over 300C with 50W.
If you don’t already have a 50W (or more) solder station I will say “why not?”. The irons get up to usable temperature much faster, the bits last longer, and soldering is much more consistent as the temperature is controlled within a degree or so of the ideal for the job. They are available on ebay at very low cost and I was staggered at the low cost of the irons and heating elements. This SMD heating plate costs a couple of percent of the Weller plate and has a higher temperature range.
In broad terms the heating plate is a piece of aluminium around 40mm diameter (or equivalent rectangular area), thick enough to take a soldering iron heater element, and set into some thermally insulating material.
My soldering iron controller is one I designed some years ago, and uses the Antex TC50 iron. I was also aware that the cheaper Zytronic irons would work – also 24V and have similar thermocouple. I did not find these but found irons for a 936 controller at around $3 – and then just the element for half that (on ebay).
In broad terms for this project you will need:
I ended up buying a few more bits than planned – and did some learning in the process that I thought I should list to save you the trouble.
My suggestion would be:
If you already have a controller – get a spare 50W iron and take the element out for the heating plate.
If you don’t have a controller – get a 50W soldering station (and a spare iron because you will want to use this for conventional soldering as well).
A last option, if you have a thermocouple type controller is to get a K type thermocouple probe and a 24V 50W cartridge heater. The latter are not expensive as they are used in 3D printers. You will have to work out the wiring.